[villagetinker]

Electric utilities use a spike strip to keep birds and other animals off sensitive equipment, I am sorry I do not recall the product name, but an internet search for bird deterrents should produce suitable results. Your biggest problem with be getting someone to mount these. You may also find ultrasonic noise (or similar) products that may or may not work, these would be much easier to mount inside the birdcage. I have seen articles with mention of reflective displays that will keep birds away, no idea if these actually work or the longevity of the item.
Finally, try a search on this site, I seem to recall previous threads, but i do not recall if there were any solutions.